1 /*
2  * Copyright (C) 2013 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include <pthread.h>
18 
19 #include <algorithm>
20 
21 #include <log/log.h>
22 
23 #include <hardware/sensors.h>
24 #include "SensorEventQueue.h"
25 
SensorEventQueue(int capacity)26 SensorEventQueue::SensorEventQueue(int capacity) {
27     mCapacity = capacity;
28 
29     mStart = 0;
30     mSize = 0;
31     mData = new sensors_event_t[mCapacity];
32     pthread_cond_init(&mSpaceAvailableCondition, NULL);
33 }
34 
~SensorEventQueue()35 SensorEventQueue::~SensorEventQueue() {
36     delete[] mData;
37     mData = NULL;
38     pthread_cond_destroy(&mSpaceAvailableCondition);
39 }
40 
getWritableRegion(int requestedLength,sensors_event_t ** out)41 int SensorEventQueue::getWritableRegion(int requestedLength, sensors_event_t** out) {
42     if (mSize == mCapacity || requestedLength <= 0) {
43         *out = NULL;
44         return 0;
45     }
46     // Start writing after the last readable record.
47     int firstWritable = (mStart + mSize) % mCapacity;
48 
49     int lastWritable = firstWritable + requestedLength - 1;
50 
51     // Don't go past the end of the data array.
52     if (lastWritable > mCapacity - 1) {
53         lastWritable = mCapacity - 1;
54     }
55     // Don't go into the readable region.
56     if (firstWritable < mStart && lastWritable >= mStart) {
57         lastWritable = mStart - 1;
58     }
59     *out = &mData[firstWritable];
60     return lastWritable - firstWritable + 1;
61 }
62 
markAsWritten(int count)63 void SensorEventQueue::markAsWritten(int count) {
64     mSize += count;
65 }
66 
getSize()67 int SensorEventQueue::getSize() {
68     return mSize;
69 }
70 
peek()71 sensors_event_t* SensorEventQueue::peek() {
72     if (mSize == 0) return NULL;
73     return &mData[mStart];
74 }
75 
dequeue()76 void SensorEventQueue::dequeue() {
77     if (mSize == 0) return;
78     if (mSize == mCapacity) {
79         pthread_cond_broadcast(&mSpaceAvailableCondition);
80     }
81     mSize--;
82     mStart = (mStart + 1) % mCapacity;
83 }
84 
85 // returns true if it waited, or false if it was a no-op.
waitForSpace(pthread_mutex_t * mutex)86 bool SensorEventQueue::waitForSpace(pthread_mutex_t* mutex) {
87     bool waited = false;
88     while (mSize == mCapacity) {
89         waited = true;
90         pthread_cond_wait(&mSpaceAvailableCondition, mutex);
91     }
92     return waited;
93 }
94